Application of superplastic forming in manufacture four-sheet sandwich panel sheetstock

Allazadeh, Mohammad Reza (2017) Application of superplastic forming in manufacture four-sheet sandwich panel sheetstock. In: 4th International Conference on Manufacturing and Industrial Technologies, 2017-05-27 - 2017-05-29, University Lisbon.

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Abstract

This presentation discusses the main processes of a superplastic forming (SPF) method to form a complex component with eight-pocket from a four-sheet sandwich panel sheetstock. Four sheets of titanium alloys were welded using resistance seam welding based on a defined pattern to manufacture a composite sheetstock of four layers. The composite sheet structures were inflated via SPF process using the Advanced Forming Research Centre’s 200 T SPF press in pockets where the sheets were not welded to each other to form a complex component. Each sheetstock was arranged to consist of four sheets: two core sheets from the same material, which create the inner structure of the panel, two skin sheets from the same material, which form the outer structure of the panel. Ti64 (Ti-6Al-4V) and Ti54 M (Ti-5Al-4Cr-4Mo-2Sn-2Zr titanium alloy sheets were used for the core sheets, whereas Ti64 and Ti6242 (Ti-6Al-2Sn-4Zr-2Mo) titanium alloy sheets were used for the outer sheets of the packs. I will also discuss the manufacture and assembly of the four-sheet packs, and briefly, explain the manufacturing processes adopted to manufacture the dies used in SPF trials. Furthermore, I will go through the applied methodology to define the SPF pressure-time curves to inflate the packs for two SPF gas feeding pipes at specific forming temperature and strain rate. Several samples from selected regions of each inflated pack were investigated via optical and scanning electron microscopy (SEM) to study whether diffusion bonding occurred between the sheets. The optical microscopy images were obtained for three different levels of magnification (x10, x20, and x50) for all samples. The GOM scanning and image analysis demonstrated that during SPF the multisheet packs underwent a degree of diffusion bonding where the adjacent sheets exhibited thickness reduction under compression forces. The thickness reduction to the component surfaces imposed by SPF was found to be up to 59% in some regions of the packs and the elongation was estimated to be up to 134%. The same procedure could be implemented to manufacture sandwich panels with more complex core configurations from sheetstock composed of more than three sheets and made of different titanium alloys